This invention relates to an improved spray machine and in particular to a spray machine that measures the thickness of a wet paint film on an article being sprayed and also controls the thickness of the paint film.
An example of a modern high quality spray machine is shown in Falcoff U.S. Pat. No. 4,614,300 issued Sept. 30, 1986. Many spray parameters are set and automatically controlled by this machine except paint film thickness.
In the spray application of many paints, a relatively thin film is formed near the edge of the article being coated and is substantially thicker in the center of the article. This difference in thickness of the paint film results in an appearance changes from the center to the edge of the article. This is a problem in the coating of articles such as auto or truck body panels in which a uniform appearance is desired and in particular is a problem for paint panels which are used as color standards in laboratories, paint manufacturing plants and automotive and truck assembly plants. In particular, rejects of paint panels to be used for color standards can be as high as 50% of the panels coated for such uses. There is a need for a spray machine and process that will uniformly apply paint to substrates and is able to monitor and correct paint flow which directly affects film thickness on the article being sprayed.